The credit bureau usually has 30 days after receiving your dispute to investigate and verify information. Typically, the credit bureau will reach out to the company that provided the information and ask them to investigate. The credit bureau is required to send you the results of the investigation within five business days of the completion of the investigation.
If you find information that is incorrect, you can file a dispute. Remember too, that items on your credit report that you don't recognize could also be potential signs of fraudulent activity — someone working to secure credit in your name for their own use. Make sure you're clear on items that could potentially be fraudulent, versus those that may simply be inaccurate.